In recent years considerable research effort has been expended in investigating the properties of hydridable materials, for example, materials having the structural formula of LaNi.sub.5. These fascinating metallic materials have the capability of absorbing large amounts of hydrogen and of releasing their hydrogen content, i.e., they are reversibly hydridable. The use of such materials as hydrogen-storage media has been visualized as being industrially important, particularly in view of the fact that the materials can absorb hydrogen to a density greater than that which is provided by liquid hydrogen. It has been found that a number of engineering problems are encountered in dealing with these materials which must be solved before satisfactory commercial devices capable of repeatedly absorbing and desorbing hydrogen for useful purposes can be devised. It is found that when these materials are subjected to hydrogen and hydrogen is absorbed that heat is generated i.e., the reaction is exothermic. However, in order to persuade the resulting metal hydride to release its hydrogen content, the hydride must be heated, i.e., dehydriding is endothermic. It had been believed that an industrial size device designed to handle substantial quantities of hydrogen would require transport of considerable quantities of heat in or out of the device depending upon whether the device was in an hydrogen-absorbing or hydrogen-releasing mode. The apparent necessity for the provision of elaborate heat transfer means in order for the device to operate would have meant a complex and expensive device with many tubes, valves and pumps.
Another factor requiring consideration was based on the observation that, during repeated hydriding and dehydriding cycles, the hydridable materials (which may initially be relatively large in particle size) crack and undergo decrepitation due to the change in volume which accompanies the hydriding/dehydriding cycles. The finely divided debris resulting from the decrepitation reaction provides additional problems in containment and complicates the design of the containment device in terms of valves, filters, etc. In addition it has been found that the fine decrepitated powder resulting from the action of the hydriding/dehydriding cycle upon the hydridable material tends to pack in the containment device with high impedance to gas flow, and undesirable increases in pressure within the device unless appropriate design steps are taken to compensate for this effect. It has been found that the problem of moving heat in and out of a device containing the hydridable material can be minimized by including a heat storage medium with a hydride former, and this forms the subject matter of U.S. patent application Ser. No. 011,194 filed Feb. 12, 1979. However, the problem of decrepitation former leading to excessive bed packing, blockage of filters, difficulty with valves, etc. still remains. In addition, the nature of the heat storage medium to be employed in connection with the hydride former is still susceptible of improvement. It is known from U.S. Pat. No. 4,110,425 that various hydrogen-storage materials of types such as magnesium, titanium, vanadium and niobium and alloys such as those of lanthanum and titanium with cobalt, nickel and iron may be bonded with various plastics and remain useful as hydrogen-storage media. It would be expected, however, that plastics would have limited strength and limited capability to resist elevation in temperature. Plastic-bonded pellets placed in beds of any substantial size and weight could thus be expected to slump or creep with accompanying reduction in bed permeability to gas flow. Furthermore, the potential for gas evolution from the plastic binder over an extended period of time exists and such gas evolution could serve as a contaminant in applications wherein hydrogen of high purity is required. The afore-mentioned patent refers in turn to U.S. Pat. Nos. 3,669,745 and 3,881,960 which are directed to electrodes for use in galvanic cells comprising mixtures of a hydride former and of another metal in powder form which are pressed and sintered. U.S. Pat. No. 4,036,944 is also directed to hydrogen sorbent compositions comprising lanthanum-nickel bonded with a plastic composition. This patent also contem-plates the inclusion of minor amounts of copper, nickel and iron metals in the plastic bonded compact. The patent reports on a failed experiment wherein 50 wt percent of copper powder was introduced with the LaNi.sub.5. After two cycles of hydrogenation the resulting compacts disintegrated.